Embodiments of the present invention relate generally to a power generation system, and more specifically, to a power generation system for using syngas generated in a gasifier to produce electricity.
An integrated gasification combined cycle (IGCC) power generation system is an advanced power generation system which integrates coal gasification technology with a high-efficiency combine cycle power generation system. A typical IGCC process mainly includes gasifying coal into medium-low heat value gas, and removing dust and sulphide in the gas to produce clean fuel gas (syngas). The clean fuel gas is then fed into a combustor of a gas turbine and burned to heat the working gas so as to drive the gas turbine to work. The exhaust of the gas turbine is used to heat the feedwater of a waste heat boiler to produce over-heating stream to drive a stream turbine to work. The IGCC power generation system basically includes parts for coal preparation, coal gasification, gas purification, and heat recovery, respectively, as well as gas turbine and steam turbine generators. High-efficiency heat recovery has important significance for the IGCC power generation system. If the energy of the high pressure and temperature gas cannot be properly reclaimed and utilized, not only the energy efficiency and the cost of the power generation system but also the environment are affected.
Currently, there are mainly two kinds of available heat recovery processes for IGCC power generation system. As for the gasification processes using dry pulverized coal as the material, usually a radiation refrigerator is used to cycle back the cold syngas in the system to quench the high temperature gas from the gasifier and reclaim the heat of the high temperature gas to produce the steam used in the steam generator. As for the gasification processes using coal-water slurry as the material, usually the high temperature gas from the gasifier is directly subjected to quench cooling and cleaning, and then fed into a gas turbine to generate power. The first processes are relatively higher in cost. The second processes are relatively lower in cost and simple in operation. However, the energy recovery efficiency of the second processes is pretty low and a great deal of energy is wasted.
Therefore, there is a need for a higher-efficiency approach for reclaiming and utilizing the energy in the IGCC power generation system.